A well completion refers to the process of making an oil or gas well ready for production. Generally, this process involves running in production tubing, and perforating or stimulating as required.
Some gas producing wells use plungers to lift production gas and liquids to the surface by providing a seal within the production tubing and utilizing downhole pressure to lift the plunger. In some cases, a plunger lift may be enhanced by increasing downhole pressure. In a relatively non-porous formation, gas or fluid may be injected into the casing-tubing annulus, which in turn returns up through the production tubing. However, in such techniques cannot be used in more porous formations as the fluid will be lost into the formation.
It is known to provide means for recirculating fluid from the annular space through to the production tubing, however such means have invariably involved a check valve which forms part of the tubing string. The disadvantage to this completion is the check valve is permanent and cannot be serviced. Once the useful lift of this valve is reached it must be disabled with the use of a tubing patch or an expensive well re-completion.
Therefore, there is a need in the art for an improved downhole valve which permits one way flow of fluids from the annular space to the tubing string while mitigating the disadvantages of the prior art.